Subterranean materials that swell or increase in volume when exposed to water are referred to as “shale”. Shale is commonly encountered during the drilling of oil well bores and these cuttings can be problematic when it degrades into smaller particles. At the surface of the well bore larger drilled cuttings can be removed by solids control equipment, but shale particles traveling up the bore will degrade into smaller particles that may adversely affect the stability of the well bore.
By incorporating a shale inhibitor in the drilling fluid or “mud”, the breakdown of shale cuttings into smaller particles can be prevented. Traditionally oil based materials have been used as drilling fluids, but environmental regulations have led to the use of aqueous fluids. To prevent adverse reactions of the aqueous drill fluids with shale, a shale inhibitor is used. A shale inhibitor minimizes tendency of shale to absorb water and degrade into small particles.
Accordingly, it is an object of this invention to provide a new and improved method of shale inhibition.